94 NATURE JULY 20, 1940, VoL. 146 LETTERS TO THE EDITORS The Editors do not hold themselves responsible for opinions expressed by their correspondents. They cannot undertake to return, or to correspond with the writers of, rejected manuscripts int,ende,d for this or any other part of NATURE. No notice is taken of anonymous communications. IN THE PRESENT CIRCUMSTANCES, PROOFS OF "LETTERS" WILL NOT BE SUBMITTED TO CORRESPONDENTS OUTSIDE GREAT BRITAIN. Classification of Sub-human Types it, may belong to the same genus as Dean Swift with a brain of 2,100 c.c., but at present many, and DURING the last fifteen years scarcely a year has even Dubois himself, still have doubts. passed but a new skull has been discovered of a type R. BROOM. of primitive man or of a higher ape allied to man's Transvaal Museum, ancestors. We are thus getting a large series of Pretoria. forms which have to be classified, and we are having June 8. much new light on the origin of man. Perhaps 1 NATlIBE, 143, 511 (1940). within a hundred years we may have all the main links between man and an anthropoid such as Dryo­ pithecus, with dozens of forms in side branches, which 10 have left no descendants. But a difficulty will arise Radioactivity of Be in nomenclature. WHEN beryllium is bombarded with deuterons, a If we have a line of forms from, say, a primitive group of protons is observed, with a range of about Eocene horse like Eohippus to an Oligocene horse 26 cm., which is attributed to the reaction Be9 like Mesohippus with every connecting link, are we (H1, H 1 ) Bet0 • It has been assumed that the product to regard all as belonging to Mesohippus ? of this reaction is the species which McMillan1 found Among the early hUQJ.an types a similar problem in a beryllium target after prolonged bombardment. is arising. Zuckerman says, "At the present time Recently, Pollard1 has reported that the activity in there does not seem to be any more reason than there question decays with a period of 350 years. This was ten years ago for separating generically from figure was obtained from the number of protons one another in classification such archaic types as emitted (which indicates the number of beryllium Sinanthropus, Pithecanthropus, Neanderthal and nuclei formed) and the number of electrons from Rhodesian man"1• If these four types are placed the decaying substance. Further, the latter author in the same genus, that genus will have to be Homo. found that the maximum electron energy was about Zuckerman further suggests that there is "no reason 0·75 Mv. to regard Java man (Pithecanthropus) and Pekin This high electron energy in combination with the man (Sinanthropus) as generically distinct. This long life at once leads to the necessity that the view was reaffirmed last year by Le Gros Clark and transition involved is at least doubly forbidden, as has just been restated by von Koenigswald and one can verify by inspection of the Sargent diagram. Weidenreich''. If this is so, it leads to the conclusion that the ground Montandon, on the other hand, considers that states for Beto and B 10 are not both S states as sug­ Pithecanthropus stands outside the Hominidre, while gested by Feenberg-Wigner and Hund•, unless a he regards Sinanthropus as a more advanced type y-ray follows the transition. In order to obtain which is definitely within the Hominid group. While further information about the radioactivity of Be10, I such a difference of opinion exists it would surely be tried to produce it by another method which would unwise to have the Pekin man called Homo pekinensis allow of its concentration in a small amount of and placed in the Hominidre, while an allied species matter. For this purpose boron was irradiated with of the same genus is called Homo erectus and placed slow or fast neutrons, which leads either to Li7 and in a different family. an a-particle, or to Be10 and a proton. It may be some years before we are in a position To make the method as sensitive as possible, about to state definitely the affinities of such types as 700 gm. boric acid were placed around a lithium target Pithecanthropus and Sinanthropus, and even to be which was bombarded with 900 kv. deuterons. The at all sure whether Sinanthropus is closely related Beto was separated chemically after 10 mgm. beryl­ to either Neanderthal man or Rhodesian man, and limn had been added as carrier. The beryllium oxide it seems to me nothing will be gained at present by was tested inside a counter so designed that even putting all these four types in the genus Homo. very soft particles could be detected. Since the Further, to place Pithecanthropus in the genus neutron source emitted, at the voltage used, and for Homo commits us to a definite conclusion which may a current of 100 µ amp., l ·8 x 1010 neutrons per or may not be correct ; and, while the majority of second, and the total dose was 700 1.1 amp.-hours, the anatomists at present agree in regarding Pithecan­ total number of neutrons passing through the sub­ thropus as a primitive type of man, there are, and have stance was 4·4 x 1014• As one electron per second always been, many who regard it as distinctly sub­ could certainly have been detected, an upper limit human. Even should it prove to be the ancestor of for the cross-section of this reaction can be found if man, I cannot see any reason why it should not be Pollard's value for the decay constant is accepted. left as Pithecanthropus, while there are very definite a becomes, as calculated from the above figures and 28 2 objections to placing it in the genus Homo. Pithecan­ the geometry, about :C:: 2 x 10- cm. ; _ this repre­ thropus with a brain of 800-950 c.c., an enlarged senting a m ean value for the inhomogeneous neutron canine tooth in the male and a diastema in front of beam. ©1940 Nature Publishing Group.